What Do the Gas Octane Ratings Actually Mean?

If you're a driver, the numbers 87, 89, and 92 should look pretty familiar to you at this point. But what do they actually mean? Here's what you should know.
Written by Marisol Pereira
Reviewed by Carrie Adkins
Nov 19, 2020
If you're a driver, the numbers 87, 89, and 92 should look pretty familiar to you at this point. You see them every time you stop for gas, and they represent the different octane ratings that are available in the U.S.
But while you may know them by heart, you might not know the meaning behind them. Basically, they're a measure of how effective the fuel is — the higher the better!
So, here's the rundown on what the octane numbers of gasoline mean, with a little help from  
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What does octane rating mean?

The octane rating is a measure of how well the fuel can resist "knocking" during combustion. The higher the rating, the better the resistance. Vehicle engines are designed to work under a controlled combustion method. A flame starts a spark that then burns through all of the fuel in the engine cylinder.
However, the high temperatures or pressure from this combustion can cause unburned fuel to ignite, and this secondary and uncontrolled combustion is what causes the "knocking." As you might've guessed, higher octane-rated gas is better at resisting these combustions. 

Which gas octane rating should I use?

As a rule of thumb, you should be using the fuel recommended by your manufacturer. You can find this information in your owner's manual. Nowadays, most vehicles are set to run on 87-octane fuel; however, this can vary depending on the model and engine, so make sure to reference your manual. 
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What happens if I use the wrong gas octane rating? 

That will depend on whether you go higher or lower. 
Since lower-octane fuel is cheaper to produce and, therefore, less expensive to purchase, you might be tempted to go with the lowest option possible. 
As noted, however, lower-octane fuel is more prone to uncontrolled combustion and therefore knocking. Modern engines are designed to be able to control this problem in a way; they can delay the primary combustion once they detect an uncontrolled combustion has happened. The result? No knocking.
However, this combustion regulation can cause the engine to underperform when it comes to power and fuel efficiency. And while going this route once in a while will most likely not have significant repercussions, if done consistently over time it can cause more severe and permanent damage to the engine. 
Perhaps the price is not your primary concern, but the health of your engine is. You want to take good care of your car, which might make you lean towards the high-octane fuel. 
There are indeed some benefits to using a high-octane fuel, the main one being better gas mileage. You might also benefit from lower CO2 emissions when performing heavy-duty tasks
such as carrying heavy loads
It's worth noting, though, that there's almost no benefit to using a higher octane rating under normal, everyday driving conditions. And the savings you'd get from the improved gas mileage can be often overturned by the high price related to a higher-octane gas. Therefore, the overall benefits might not justify the higher expense.

Protecting your car

If you happen to put the wrong fuel octane rating in your car, don't panic. Even if something goes wrong, your insurance might be able to step in and sort things out. For the best rate on
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And to ensure you always have the lowest rate, Jerry will send you new quotes every time your policy comes up for renewal, so you’re always getting the coverage you want at the best price.
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